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In this work, the impact of alloying calcium into Mg-5Al-4Sn-based alloys on the microstructure and pitting corrosion resistance of these alloys is characterized. Electrochemical results showed that the corrosion potential (Ecorr), pitting potential (Epit), film stability, and film and charge transfer resistances of the investigated specimens increased when the calcium content in the alloys was increased up to 1.0 wt.%. Surface characterizations showed that the addition of calcium fosters the formation of a passive film, which contains a mixture of oxides/hydroxides of aluminum, magnesium, and tin that are uniformly distributed on the alloy surface. Notably, calcium addition also promotes grain refinement, and a more uniform distribution of the secondary phases in the alloy structure, boosting passive film formation on the alloy surfaces. These benefits could foster greater pitting resistance in the Mg-5Al-4Sn-based alloy system. [ABSTRACT FROM AUTHOR]

The selection of lubricants depends on the deformation mechanism of each process which significantly affects the surface roughness. In the incremental sheet forming process, there has been little attention on this aspect. This study investigates the influence of lubricants and lubricating methods on the surface quality and geometric accuracy during the two-point incremental forming process (TPIF). By using five different lubricants and two lubricating methods, the experiments were conducted to deform the 45°-cone parts with an aluminum sheet. Then, the formed parts were analyzed in terms of surface roughness and geometric accuracy. The morphology of the formed surfaces was also observed by using the scanning electronic microscope (SEM). The experimental results showed that the mixed lubricant (graphite powder + MSo2 + machine oil) greatly improved the surface quality and geometric accuracy. Using vegetable oil as an alternative lubricant for the TPIF process induced low cost and environmental effects but provided the surface quality similar to machine oil. [ABSTRACT FROM AUTHOR]